In copending parent patent application Ser. No. 07/906,573 filed Jun. 30, 1992, small articles such as drycell batteries, lipstick containers, lip balm containers and the like are labeled with high quality, thin film polymeric labels. A strip of label material is fed to a label transport drum, which has an outer surface with a plurality of predetermined label areas on which labels are retained as the drum rotates. The labels are initially fed as a strip onto the drum surface, and then cut on the drum surface into labels of predetermined size.
As each label moves with the rotating drum in its respective label area, an adhesive is applied onto the area adjacent the leading edge of the label to give the leading edge a tacky quality to the edge. A predetermined amount of solvent is evenly applied onto the area adjacent the trailing edge of the label so as to dissolve a portion of the treated surface of the label. The label moves to an article wrapping position where small articles, such as drycell batteries, are wrapped, securing first the leading edge to the article, followed by overlapping the trailing edge onto the leading edge so that the solvent positioned on the trailing edge of the label creates a solvent-seal bond. The labels are then heat shrunk over the articles. The apparatus provides for high quality cylindrical labeling of small articles such as drycell batteries using thin film, polymeric labels, e.g., typically less than 0.0035" thickness.
As disclosed in the copending parent application, a predetermined amount of solvent is applied to the area adjacent the trailing edge of the label by rotating a wiper member at a surface speed different from the speed of the label transport drum. The speed differential between the wiper tip and drum has been found to aid in applying solvent in a predetermined pattern on the trailing edge of the smaller labels used for wrap around labeling of small cylindrical articles such a drycell batteries. It has been found advantageous to use a maximized speed differential by controlled application of solvent through a static wiper spaced from the drum periphery. The use of a static wiper, however, requires some means for positioning the trailing edge of the label outward from the drum periphery to engage the outwardly spaced static wiper member.
Protrusions, ridges and other similar means could be used to position the trailing label edge outward from the drum surface to engage an outwardly positioned static wiper. In this construction, however, any article delivery mechanism, such as a chain conveyor or star wheel assembly, must have its article discharge area spaced outward from the drum surface so that the delivery mechanism will not engage the outwardly positioned trailing edge and interfere with labeling. This spacing creates a "drop-off" from the delivery mechanism onto the drum surface. This drop-off could pose problems in article delivery onto the label transport drum for wrap around labeling because the articles should desirably be fed tangentially and smoothly onto the surface of the drum without interfering with the label.
When labeling larger articles where the trailing edge is positioned outward from the drum periphery, such as sometimes occurs when labeling commercially available soft drink containers or large metallic cans, this drop-off is not critical to labeling quality because the containers are typically lightweight compared to their size, and often the desired label quality often is not high. The drop-off is relatively unnoticed.
With smaller cylindrical articles, the drop-off would be more pronounced compared to the size of the label and article. The drop-off makes labeling of these smaller articles more difficult because the smaller article drops onto the drum surface, instead of being tangentially and smoothly delivered thereon. In some cases, where the article drops onto the drum, the article becomes skewed relative to the label, resulting in poor quality labeling.
When the smaller article is a dry cell, such as formed from a metallic casing, the relative difficulty of labeling is increased even more. Typically, these metallic articles, such as drycell batteries, are heavier than other articles of similar size, making the articles more difficult to label correctly. This labeling difficulty could be even more pronounced when the heavier articles engage a pressure plate that is used for guiding the articles against the label transport drum. When using a pressure plate, it is more desirable to move the articles in tangential, spinning engagement between the pressure plate and the drum surface. This is made even more difficult by the drop-off from the delivery mechanism onto the drum.
The copending parent application also discloses a rotary pad print head for applying a cold adhesive onto the leading edge of a label. As the printhead rotates, an adhesive print pad engages a gravure roller having adhesive applied thereto. The print pad preferably rotates at the same surface speed as the drum and is timed so that the pad prints the adhesive onto the area of the label adjacent the leading edge.
It has been proposed to apply adhesive to the gravure roller by means of a dip bath where a portion of the gravure roller is immersed in a bath of cold adhesive. As the gravure roller rotates, it picks up adhesive from the bath. A doctor blade then removes excess adhesive.
The cold adhesive is viscous and difficult to control, and a dip bath was seen as one means to supply this viscous adhesive onto the gravure roll for transfer to the print pad. This system, however, can cause unwanted adhesive splashing and dripping, and an uncontrolled adhesive feed onto the gravure roller. The adhesive in the delivery lines and possibly the adhesive in the dip bath also can become stagnant, especially during slow production periods, making the already viscous adhesive even more difficult to control.
An adhesive system, which feeds adhesive directly onto the gravure roller, such as a reciprocating pump, also can become stagnant when production has slowed or stopped altogether. It would be more desirable to supply the cold adhesive in a more controlled manner onto the gravure roll as well as provide a means for minimizing stagnation of the cold adhesive in the delivery lines when production has slowed.
Additionally, it has been found that cutting on the label transport drum, such as disclosed in the copending, parent application, is not as desirable as heretofore believed when labeling small, cylindrical articles typically under about 1.75 inches diameter with small, thin film polymer labels. Poor film cutting can occur when cutting on-drum. On-drum cutting may also be more difficult if the area of the drum surface where the trailing edge of a label lies is positioned generally outward from the drum surface for engaging a fixed wiper. This outwardly extended area on which the trailing edge rests would receive the cutting blade, and thus, cutting on this raised surface could create inaccurate cutting. A separate cutting element that is positioned on the drum surface would also interfere with subsequent labeling because the article would have to roll up and over the drum positioned cutting element, making labeling of a small article difficult.
It is proposed to use off-drum cutting so that cutting on the label transport drum is no longer required. Off-drum cutting, however, requires precise placement of cut labels onto predetermined label areas defined on the drum surface so that leading and trailing edges are accurately positioned to ensure precise high quality labeling. It has been found that a cutting drum which is positioned close to the peripheral surface of the label transport drum provides for adequate off-drum cutting. For smaller cut labels, such as used with dry cell batteries, it has been found that the cutting drum should be as close as 0.010 to about 0.050 inches and preferably as close as 0.010 to 0.025 inches to ensure adequate transfer of the label onto the label transport drum at high operating speeds. If the cutting drum were positioned a greater distance from the label transport drum, the light weight, small label may not transfer properly.
These close distances, however, are unobtainable with many conventional cutting apparatus when the label transport drum includes structure for positioning the trailing edge of a label outward from the drum surface a sufficient distance to engage a static wiper. This positioning structure could extend as far as 0.040 or more inches from the drum periphery. This distance is necessary to ensure proper label engagement with a wiper, and sufficient clearance between the wiper and peripheral surface of the label transport drum. As the label transport drum and cutting drum rotate, the positioning means could violently engage the cutting drum during high speed operation, causing label misplacement during label transfer onto the label transport drum.
Small differences in web feed, sometimes as little as one-sixteenth of an inch, also could cause improper film positioning during cutting, thus creating an inaccurate cut point. As a result, the printed indicia and other identifying logos or indicia on the cut labels would be improperly aligned. It is necessary then, to ensure precise off-drum cutting on a cutting drum and subsequent, accurate transfer of cut labels onto the label transport drum for wrap around labeling of small cylinder articles, which typically are less than about 1.75 inches diameter.